Detection of engine failure in a multi-engine aircraft

Abstract

Primary logic (116-128) for engine failure detection in a multi-engine aircraft is based on thresholds for engine torque (Q), gas generator speed (NG), power turbine inner stage temperature (T5), power turbine speed (NF), throttle setting (PLA), and throttle manipulation (PLADOT). Subroutines for return to dual engine operation (110), backup of the primary logic (200,300) and remaining engine failure (200) are disclosed.

We claim: 
     
       1. A method of detecting an engine failure in a multi-engine aircraft having at least two engines each of which includes a gas generator and a power turbine having an inner stage and is operated in dependence on the angle of a power lever, and an electronic engine control unit for each engine so that the engine associated with the respective control unit constitutes a local engine, and each remaining engine constitutes a remote engine, comprising: sensing whether the power lever angle for the local engine (PLA) is between a first value and a second value;   sensing whether the difference in torque between the local engine and the remote engine(s) exceeds a first threshold;   sensing whether the gas generator speed for the local engine (NGDOT) is decreasing at a rate in excess of a second threshold;   sensing whether the power turbine inner stage temperature of the remote engine (DT5RMT) is increasing, steady, or decreasing at a rate less than a third threshold;   sensing whether the power turbine speed of the local engine (NF) is below its reference speed by a margin;   sensing whether there is not advertent pilot manipulation of the power lever associated with the local engine; and   signaling failure of the local engine in response to the simultaneous satisfaction of all of the above conditions for X seconds.   
     
     
       2. The method of claim 1 wherein: the first value is 48°;   the second value is 62°;   the first threshold is 20%;   the second threshold is -5%/second;   the third threshold is -30° C./second;   the margin is 1%; and X is 0.2.   
     
     
       3. The method of claim 1 wherein the local engine is allowed to be reset in response to the simultaneous satisfaction of the following conditions for Y seconds: the gas generator speed for the local engine is increasing; and   the gas generator speed for the local engine is greater than a fourth threshold.   
     
     
       4. The method of claim 3 wherein; Y is 0.2; and   the fourth threshold is 57%.   
     
     
       5. A method of detecting an engine failure in a multi-engine aircraft having at least two engines each of which includes a gas generator and is operated in dependence on the angle of a power lever, and an electronic engine control unit for each engine, comprising, for each engine that is associated with the respective control unit to constitute a local engine: sensing whether the power lever angle for the local engine (PLA) has at least a predetermined value;   sensing whether the gas generator speed of the local engine (NG) is less than or equal to a threshold;   sensing whether the gas generator speed for the local engine (NGDOT) is decreasing for Z seconds; and   signaling failure of the local engine in response to the simultaneous satisfaction of all of the above conditions.   
     
     
       6. The method of claim 5, wherein; the predetermined value is 48°;   the threshold is 52%, and   Z is 0.2.